The present invention relates to electrical isolation circuits and in particular an isolation circuit which utilizes at least two signals to represent the signal to be isolated.
Isolation circuits have utilized many different isolation devices, such as electromagnetic coils and optical couplers. Electromagnetic coils have been used mainly to isolate analog signals by coupling the entire analog signal. Optical couplers generally have a light emitting device coupled to a photo sensitive device and have been used to couple digital pulses by techniques including optical coupling of the entire pulse. Optical couplers have also been used to isolate analog signals by measuring received light intensity and by converting analog signals to pulse width modulated, pulse amplitude modulated, and pulse frequency modulated digital signals where the entire signal is coupled through the optical coupler. Coupling an entire pulse through an optical coupler required that the light emitting device and photo sensitive device have substantially equal, time stable and sharply defined turn-on and turn-off time characteristics.